Social networks can be used in 2 main ways for your business.
1) Social Presence
With a social presence you have accounts with the social network and use these accounts to publish content linking back to your site. You encourage people to follow you on these social networks so that as you publish content it is pushed out to your followers.
If you use Twitter and Facebook Pages you might like to consider linking these two accounts. This allows you to enter the information in one of the services only and it is automatically pushed to the other service. Please see the settings of Twitter or Facebook to set this up. Alternatively you can use a service such as Hootsuite (www.hootsuite.com) which can publish to both platforms.
If you have our news module on your site then we create a RSS feed. You can then use a service such as TwiiterFeed (www.twitterfeed.com) to pull content from this RSS Feed and publish it to your Twitter A/C or Facebook Page.
2) Social Sharing
Social sharing are links on your web pages that allow users to share the page with their followers on a variety of social networks. These links can be easily setup using a service such as AddThis (www.addthis.com).